Cup-shaped grid having concavity containing annular rib surrounding coined aperture region

ABSTRACT

A first grid electrode for use in a plural electrode electron gun comprising a cathode and related first and second grid electrodes having compatibly shaped adjacent functional surfaces. The apertured functional portion of the first grid is formed in a concave manner with the concavity thereof facing away from the cathode; the first grid having an aperture concavely coined within the concavity. The superfluous material resultant from the aperture coining is utilized adjacent thereto in forming an axially oriented annular rib which is shaped to protrude within the concavity.

United States Patent 1191 Russell's 1 Oct. 23, 1973 1 CUP-SHAPED GRID HAVING CONCAVITY 2,484,721 10/1949 Moss ..313/82 R CONTAINING ANNULAR RIB 2,554,170 5/1951 Bruck ..3l3/86 X SURROUNDING COINED APERTURE 2,732,511 l/l956 Dichter ..313/86 X REGION 2,862,129 11/1958 Van Dorsten ..3l3/86 3,254,251 5/1966 Hughes ..3l3/82 RX [76] Inventor: Chris F. Bossers, Seneca Falls, NY. 22 Filed: Sept 13 1971 Primary ExaminerRobert Sega] Attorney-Norman J. OMalley et al. [21] Appl. No.: 179,784

Related US. Application Data 1 1 ABSTRACT [62] Division of Ser. No.- 14,504, Feb. 26, 1970, Pat. No. A first grid electrode for use in a plural electrode elec- 3,628077- tron gun comprising a cathode and related first and second grid electrodes having compatibly shaped adja- [52] US. Cl. 313/86 cent functional surfaces. The apertured functional [51] Int. Cl. H0lj 29/02 tion of the fir t grid is formed in a concave manner Field Of Search 313/69 70 with the concavity thereof facing away from the cath- 313/32 85 R ode; the first grid having an aperture concavely coined within the concavity. The superfluous material resul- 1 References Cited tant from the aperture coining is utilized adjacent UNITED STATES PATENTS thereto in forming an axially oriented annular rib 2,135,941 11/1938 Hirmann 313/85 R which is Shaped protrude within the 2,441,315 5/1948 313/85 R x 1 Claim, 4 Drawing Figures 2,877,369 3/1959 313/85 R X 2,957,106 10/1960 313/85 R X h 3,453,473 7 1969 0e55,, 313/82 R CUP-SHAPED GRID HAVING CONCAVITY CONTAINING ANNULARRIB SURROUNDING COINED APER'IURE REGION CROSS-REFERENCE TO RELATED APPLICATION BACKGROUND OF THE INVENTION This invention relates to cathode ray tubes and more particularly to a first grid electrode formed for use in an electron gun structure.

In certain types of CRT electron guns most of the cathode structure is usually encompassed by a cupshaped first grid electrode wherein the apertured closed end is usually planar. In those instances where a-thin first grid aperture is desired, a coined aperture shaping may be employed wherein the superfluous material resultant from coining is usually accommodated in an annular take-up-rib formed adjacent the coining which promotes flattening of the aperture. This rib is also intended to function as a strengthening structure in an endeavor to minimize in-and-out expansive and contractive thermal movement of the substantially planar closed end' of the grid, but positional stability is difficult to maintain when a planar surface is adjacent the heated cathode. Any in-and-out movement of the functional planar grid surface is deleterious as it directly affects consistent spacing between the first and second grid apertures. Since the critical spacing between the apertured surfaces of the first and second grid electrodes is usually of a relatively close dimension, it has been conventional practice to form the first grid rib inwardly away from the outer surface thereof.

In first grids employing a regular unc oined aperture, one or more inspection openings have been sometimes incorporated into the sidewall or skirt portion of the first grid electrode to facilitate visual inspection and adjustment of the spacing between the cathode and the first grid aperture. When coined apertures are employed, the inherent inwardly extending take-up-rib obstructs the view of the cathode-grid aperture spacing and thereby eliminates the desired utility of the inspection opening.

OBJECTS. AND SUMMARY OF THE INVENTION It is an object of the invention to reduce the aforementioned disadvantages and to provide an improved first electrode for use in a cathode ray tube electron gun structure wherein the functional surface of the first grid electrode is discretely formed.

Another object is the provision of a first grid electrode structure wherein the apertured end closure and skirt portions are formed in a manner to achieve and maintain accurate spacing of the cathode positioned therein.

The foregoing objects are achieved in one aspect of the invention by the provision of an improved first grid electrode for use in an electron gun comprising a cathode and a plurality of sequential electrodes including first and second grid electrodes having adjacent related functional surfaces. The functional portion of the first grid is formed in a concave manner to provide a con cavity of defined depth. A beam defining aperture therein has the immediately surroundingmaterial reduced in thickness by concave coining oriented within the concavity. The superfluous material resultant from the coining is utilized in forming an axially oriented annular rib which protrudes within the concavity adjacent the coined aperture. Thus, there is no rib material extending beyond the flattened surface of the aperture toward the cathode.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a cathode ray tube wherein the invention is utilized;

FIG. 2 is an enlarged sectional view of a portion of the electron gun structure employing the invention;

FIG. 3 is a plan view illustrating the end closure portion of the first grid electrode taken along the line 3-3 of FIG. 2; and

FIG. 4 is a sectional view of another embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT For a better understanding of the present invention, together with other and further objects, advantages, and capabilities thereof, reference is made to the following specification and appended claims in connection with the aforedescribed drawings.

With reference to the drawings, thereis shown in FIG. 1, a cathode ray tube 11 having an axis 12 and comprising an envelope l3 whereof the face plate or viewing panel 15 has a cathodoluminescent screen 17 formed on the inner surface thereof. Positioned within the neck portion 19 of the envelope is at least one electron gun structure 21, not detailed, which includes a cathode and a plurality of sequentially arranged electrodes. These cooperating electrode elements are formed and spaced to provide the source, acceleration and control of the electron beam 23 which is controllably deflected by coils 25, positioned externally of the envelope, to effect predetermined impingement on the screen 17 and thereby provide an image display raster therein. As shown, the axes of the electron gun 21 and the tube 11 are substantially coincidental, but such axes relationship is not intended to be limiting.

In referring to FIG. 2, there is shown an enlarged sectional view of the rear portion of the electron gun structure '21 which is oriented in the neck portion 19, not shown. This portion of the electron gun 21 comprises a thermionic cathode structure 27 having an external electron emissive area 29 and an internally positioned heating element 31. By way of illustration, a substantially cup-shaped first grid electrode 33 is shown but is not to be considered limiting. This first grid is positioned to encompass at least part of the cathode 27. A second electrode 35 is oriented in spaced axial relation ship to the first grid 33, and a first anode electrode 37, a portion of which is shown, is spacedly positioned therebeyond. Conventional means, such as studs and glass rods, are utilized to support these several electrodes in axial alignment, but since such support means are not part of the invention they are not illustrated in the drawings. To add clarity to the description, certain illustrative dimensions will be given in the course of this specification, but in no manner are they to be considered limiting.

ln greater detail, with reference to FIGS. 2 and 3, the first grid electrode 33, which for example may be formed from non-magnetic stainless steel of substantially 0.007 inches thickness, has a substantially cylindrical skirt portion 39 and a functional area or end closure portion 41 which is integrally joined to the skirt portion 39 at a common peripheral transition rim 43. The fucntional or closure portion 41, which has a material thickness 1, is formed as an inwardly oriented concave shaping providing a concavity 44 of defined depth e to impart strengthened positional stability to the closure having inner and outer surfaces 45 and 47 respectively. A beam shaping aperture 49 is formed as a substantially axially oriented bore in the concave closure portion 41, and the closure material thickness immediately surrounding the aperture 49 is reduced by a concave coining 48 within the concavity 44 relative to the outer surface 47 of the closure portion 41. By this coining operation a beneficial reduction in thickness of material t" is achieved at the aperture 49. This reduced aperture thickness in conjunction with the distance 0, such as 0.005 inch, between the emissive portion 29 of the cathode 27 and the inner surface 45 of the first grid functional or closure portion 41 constitutes a critical dimension t) which is desirably small, being in the order of 0.008 inch. The concave coining 48 or gradual reduction in material thickness is effected within a substantially axially oriented circular area diametrically dimensioned by a which may be approximately 0.090 inch. The superfluous material displaced as a result of the coining operation is utilized in the forming of an axially oriented annular support rib 51 which protrudes within the concavity 44 as part of the outer surface 47 of the closure adjacent the coined area 48. This annular rib 57 is laterally defined by a diametrical dimension b having a value such as 0.150 inch. It has an overall height d of approximately 0.015 inch which is less than the overall concavity depth e of the closure 41, that being approximately 0.020 inch. At no time should the support rib 51 extend above the plane of the peripheral rim 43.

At least two substantially diametrically opposed inspection windows 55 are formed in substantially the skirt portion 39 at substantially the peripheral transition rim 43. By being edged into the periphery of the closure portion 41 these window areas 55 afford ample unobstructed viewing of the cathode area 29 in relation to the inner surface of the beam forming aperture region 49. By this means the cathode can be accurately positioned and inspected.

A second grid electrode 35 having a material thickness such as 0.007 inch is spacedly positioned relative to the concave outer surface of the first grid electrode 33, as denoted by the spacingfof approximately 0.025 inch. The second grid functional or end closure portion 57 has inner and outer surfaces 59 and 61 respectively with a substantially uniform material thickness therebetween. An axially related central portion 63 having an axial aperture 65 therein is formed to protrude outwardly from a substantially flat circumferential portion 67, by a dimension n, toward the concavity of the first grid electrode 33. This protruding dimension n may be for example 0.020 inch, which in conjunction with the spacing of f provides the desired interelectrode aperture spacing s. In keeping with the invention, the dimension u may be larger or smaller than the spacingf depending on the inter-electrode spacing s desired. In this instance, the central protruding portion 63 has a diametrical dimension v which is less than the diametrical dimension b of the first grid annular support rib 51,

but there may be grid relationships wherein v is greater than b.

The electron gun structure 21 further comprises a substantially cylindrical first anode electrode 37 located screenward of and in spaced axial relationship to the second grid electrode 35. Additional sequentially positioned cooperating electrodes may be included in the gun structure in accordance with the particular gun design utilized.

With reference to FIG. 4, there is shown another embodiment ofa first grid electrode structure 33' wherein the skirt portion is eliminated. Such grid construction is sometimes utilized in certain types of gun assemblies. By this invention the functional portion 41' is concavely formed to provide a concavity 44' having a defined depth e. The coined aperture 48 and the supporting rib 51 are structures similar to counterparts already described. The annular rib 51 protrudes within the concavity 44', but does not extend above the plane of the peripheral rim 43'. A first grid of this structure is suitably positioned by support means, not shown, which are extended in a conventional manner beyond the peripheral rim 43' to be embedded, for example, in a commonly employed glass support means, not detailed.

Thus, an improved first grid electrode for use in a cathode ray tube electron gun structure is provided wherein the functional closure surface 41 of the first grid electrode 33 is discretely formed to effect a stabilized cooperative relationship with the compatibly formed second grid electrode 35. Additionally, the first grid electrode 33 is formed in a manner to facilitate optical adjustment of the cathode thereby expeditiously effecting cathode-to-first-grid electrode spacing of desired accuracy. While the aforedescribed structural recitations are applicable to cathode ray tube electron guns of any size, they are particularly advantageous in construction miniaturized gun assemblies having critically close electrode spacings and utilizing electrode apertures of small sizes, for example, those of 0.020 inch and smaller.

While there has been shown and described what are at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.

What is claimed is:

1. A first grid electrode for use in a cathode ray tube electron gun formed for subsequent operational positioning between a cathode and a second grid electrode having an end closure portion with an aperture therein, said first grid comprising in combination:

a substantially cup-shaped member formed of a substantially cylindrical skirt portion joined to a closure portion at a common peripheral transition rim therebetween, said closure portion being shaped as a substantially circular concave functional area having an axis therethrough and a defined concavity depth with a beam control aperture formed as a substantially axial bore through the concave bottom thereof, the material thickness immediately surrounding said aperture being of reduced thickness resulting from concavecoining of the aperturerelated material within to the concave surface of said concavity; and an axially oriented annular rib formed in said concave closure area in a manner to protrude within said concavity circumferentially adjacent said coined aperture therein, said protruding rib having a height not exceeding the depth of the concavity of said functional closure area.

"1- 3 UNITED STATES PATENT OFFICE 569 CERTIFICATE OF CORRECTION patent 3,767,953 Dated October 23, .1973

lnventm-(s) Chris F. Bossers It is certified that error appears in the above-identified patent and that saidLetters Patent are hereby corrected as shown below:

Please add the following to the front page:

[73] Assignee: GTE Sylvania Incorporated Seneca Falls, New York Column 4, Claim 1, Lines 60 and 61: Change "aperturerelated" to aperture-adjacent Column 4, Claim 1, Line 61: Delete "to" Signed and sealed this 16th day of April 1971+.

(SEAL) Attest:

EDWARD MELETCHERJR. c. MARSHALL DANN Atte sting Officer Commissioner of Patents 

1. A first grid electrode for use in a cathode ray tube electron gun formed for subsequent operational positioning between a cathode and a second grid electrode having an end closure portion with an aperture therein, said first grid comprising in combination: a substantially cup-shaped member formed of a substantially cylindrical skirt portion joined to a closure portion at a common peripheral transition rim therebetween, said closure portion being shaped as a substantially circular concave functional area having an axis therethrough and a defined concavity depth with a beam control aperture formed as a substantially axial bore through the concave bottom thereof, the material thickness immediately surrounding said aperture being of reduced thickness resulting from concavecoining of the aperture-related material within to the concave surface of said concavity; and an axially oriented annular rib formed in said concave closure area in a manner to protrude within said concavity circumferentially adjacent said coined aperture therein, said protruding rib having a height not exceeding the depth of the concavity of said functional closure area. 